The present invention relates in general to an optical deflector device using a solid deflector for deflecting a light beam, and more particularly to an art of deflecting a light beam in a waveguide formed of an electrooptic material, by utilizing the electrooptic effect of the electrooptic material.
An optical device for deflecting a light beam within a given angular range is used in various devices such as a laser-beam printer that uses a low-power laser to produce image-forming charges, and a bar code reader that reads combinations of printed bars. Known as typical examples of such a light deflector are a polygon mirror and a hologram scanner. These deflectors employ mechanical moving parts such as a rotary mechanism and a device for driving the rotary mechanism. Thus, these deflector devices using such mechanical parts tend to be complicated in construction, large-sized, and are not satisfactory in duration.
In view of the above inconveniences encountered in the prior art light deflecting devices, it is considered possible to use a solid deflector element which employs a transparent substrate of LiNbO.sub.3, SiO.sub.2, etc. On one of opposite primary surfaces of the substrate, a two-dimensional waveguide is formed to guide or conduct waves of a light beam. For improved operation of the deflector, it is considered desirable to provide the waveguide with a portion which functions as a concave lens. Described more specifically, such a two-dimensional waveguide formed on the substrate incorporates a deflector of various types for deflecting a beam of light, utilizing the electrooptic effect, or the effect of ultrasonic light diffraction. However, the deflecting capability of such a deflector portion of the waveguide is limited. For this reason, it is considered necessary to form the waveguide with an integral concave-lens portion which is located downstream of the deflector portion, to receive the light beam deflected by the deflector portion, and to boost or amplify an angle of deflection of the light beam. However, the concave-lens portion or deflection-amplifying portion tends to enlarge the substrate. Although it seems possible to substitute a separate concave lens for the integral concave-lens portion, the size of the deflector device as a whole is also increased.